Adapantus excavatus Heller 2019, n. sp.

Adapantus excavatus n. sp.

(Fig. 5 A, 6 A–C, 7 A–D)

http://lsid.speciesfile.org/urn:lsid: Orthoptera.speciesfile.org:TaxonName:505232

Holotype: male, SAO TOME & PRINCIPE: Príncipe, near Bom Bom Island Resort (1°41'N, 7°24'E), 20 m a.s.l., 24–27 iv 2018, leg. Martina Heller; MfN.

When we collected the animal (habitus Fig. 5 A) on Príncipe, we expected to have found Adapantus transmarinus, known for this island from literature (see above). However, it differs distinctly from this species and has to be described as a new species which may even not be the sister species to transmarinus.

Diagnosis. Differs from all other Adapantus species by the tips of the male cerci which do not end in a spine, but are excavated (Fig. 6 A).

Description (following the concept of Naskrecki, 2008a).

General. Body of medium size (habitus Fig. 5 A)

Head. Antennae more than twice as long as body; fastigium of vertex triangular, nearly reaching apex of antennal sockets (Fig. 7 A), grooved dorsally; frons flat. Scapus with small apical spine.

Thorax. Humeral sinus of pronotum absent; lateral lobe wider than high; upper side of pronotum concave; anterior and posterior edge of prozona convexly rounded (Fig. 7 A); pronotum surface weakly granulate. Prosternum armed with two short spines.

Legs. Genicular lobes of front and hind femur (Fig. 6 C) armed with spines on both sides, mid femora with spines on inner side only; mid tibia dorsally unarmed.

Wings. Tegmina distinctly surpassing apex of abdomen; left stridulatory area coriaceous, with a large cell, shaped as mirror (Fig. 7 C); right stridulatory area with very large mirror (Fig. 7 D). Stridulatory vein very thick (Fig. 7 A, C), stridulatory file weakly bent, flat, with ca. 135 lamelliform teeth, 3.1 mm long (Fig. 7 B). Hind wing as long as tegmina.

Abdomen. Cercus bent in apical third; apex of cercus slightly thickened, excavated (Fig. 6 A); subgenital plate with small, triangular apical incision; stylus cylindrical, more than 3 times as long as wide (Fig. 6 B).

Coloration. Coloration brown and green, sometimes mottled (Fig. 5 A); face light brown, without darker markings; hind wing fumose.

Measurements (in mm). Body w/wings 32; body w/o wings: 29; pronotum: 5.5; tegmen: 25; hind femur: 18.

Etymology. The specific epithet excavatus refers to the shape of the cercus (adjective, masculinum).

Bioacoustics. See below, part B.

A. excavatus differs from A. transmarinus, the other species from São Tomé and Príncipe, not only in cercus shape, but also in the armature of the hind knees. A. transmarinus belongs to a group of species without any spines, while A. excavatus has spines as found in another species group. The new species differs in its stridulatory organs also distinctly from the three species of the genus described by Naskrecki (2008a). Comparing the other species of the genus, A. bardus Karsch (see also Naskrecki 2008a), osorioi Bolivar, excavatus, transmarinus and some other species (according to photos in OSFO) have a very strong stridulatory vein and a more or less distinct mirror in the left tegmen, whereas Naskrecki’s three new species have a weak stridulatory vein and no indication of a left mirrorlike structure. The characters are clearly recognisable in Naskrecki’s excellent figure 8 and also mentioned in his text. Beier (1962), however, mentions the presence of left and right mirrors as a characteristic of the genus Adapantus. The difference in the stridulatory organs is so distinctive that it may justify a subgeneric subdivision. The left mirror is an important predictor of a species’ carrier frequency (Montealegre-Z et al., 2017) and large morphological differences may indicate differences in the communication system.